To win a boss fight, tap as fast as you can in the allotted time.
F**k Off Power is displayed at the top left, time remaining displayed at the top middle, and number of rewards displayed at the top right.
Each time you fill the boss damage bar you will earn more rewards in the Police trunk for completing the season.
TIP: You can tap faster if you use multiple fingers.
Increase your F**k Off Power by upgrading certain characters.